Forty years ago the provision of water was a public service that was taken for granted in many parts of the world. Few people thought water could ever be privatised and sold for private profit.

Twenty years ago, health was widely perceived as a public service – but since then health systems have suffered from creeping marketisation and privatisation in most countries. In recent years the World Economic Forum (the exclusive club that meets in Davos) has been buzzing with the idea that the next big frontier for privatisation is education.

There are trillions of dollars of public funding spent on public education systems and this is money that privatisers are keen to get a share of. After all, claiming public money is a great route to guaranteeing higher private profits.

In most countries we still take for granted that there is a public education system which provides for the majority of children. There has always been a small elite who perpetuate their privilege by sending their children to exclusive private schools for high fees. But in recent years we have seen the emergence of private schools that target the middle class.

Pearson, the largest education company in the world, has spent hundreds of millions of dollars to purchase chains of such schools in India, Brazil and South Africa. And most recently there is the new phenomenon of what should be called ‘for-profit low quality private schools’, touted byThe Economist as the solution to expanding education provision in developing countries.

Except this is a lie. Low-fee private schools do not extend access to the any of the 58 million children out of school around the world. Rather they attract children (especially boys) who are already in government schools, whose parents can afford to pay for what they see to be an advantage. The effect is to actively undermine government schools (as their funding is often based on the number of children enrolled).

And the children who go to these low-cost private schools do not actually get a better education. When controlled for socio-economic status you find that the same children would have done just as well staying in the public education system. Basically, it is a clever con that exploits people’s aspirations. You attract the students who will do well anyway and then claim that your school has made the difference.

Just fifteen years ago there was a sustained campaign for the abolition of user fees in primary education. Research at that time showed that under the influence of the World Bank over 92 countries were charging children to go to primary school – often just a few dollars a month but enough to make schools inaccessible to the poorest children.

Successful national campaigns led to the abolition of fees in countries like Kenya, Burundi, Malawi and Ghana. In Kenya alone, over 2 million children enrolled in school the following year – children who could not afford to go to school before. In the light of this it is patent nonsense to say that privatisation can help make progress towards the goal of universalising access to basic education.

Nor do they help to improve quality. It is widely recognised that the biggest determinant of quality learning is the quality of teachers. But these schools make their profit by employing untrained people as teachers, paying them less than a third of a professional teacher’s salary. Creating a cheap labour force is not going to improve learning outcomes.

Now is the time to act because there are aggressive forces pushing the privatisation of education. New commercial chains of for-profit schools like Bridge International are being funded to expand in Africa by hedge fund speculators and American billionaires – with just this one company planning to open a new school every three days (the larger the scale of operations the lower the unit costs).

This is driven by greed and ideology not by evidence, and it needs to be stopped. Strict government regulation of the private sector providers is part of the solution and some progress is being made on this with the support of the UN Special Rapporteur on the Right to Education..

But we also need to challenge those who are using public money to support such privatisation. Three recent reports show that DfID is increasingly channelling its public funding to support the privatisation of education around the world. This is contributing to mounting violations of the right to education, increasing discrimination and undermining the huge potential of education to be an equalising or transformative force.

We know how to improve public education – there are no great mysteries about it. We need well financed public education systems that employ well-trained teachers working with manageable class sizes in accountable schools. Decades of IMF-enforced austerity have undermined peoples’ confidence that public education can be well financed.

But recent work on tax justice shows that by removing harmful tax incentives and challenging aggressive tax avoidance, over $200 billion could be generated every year. That is five times more than is needed in extra resources to guarantee high quality public education for every child in every country.

Quality public education, free at the point of use is affordable – but unless we act now to defend it we will find that this simple foundation of a just society has been stripped away.